Heat-developable diazotype material



United States Patent 3,525,619 HEAT-DEVELOPABLE DIAZOTYPE MATERIAL Siegfried Scheler, Wiesbaden-Schierstein, and Johannes Munder, Wiesbaden-Biebrich, Germany, assignors, by mesne assignments, to Keuifel & Esser Company, Morristown, N .J.

No Drawing. Filed Sept. 8, 1966, Ser. No. 577,835

Claims priority, application Germany, Sept. 10, 1965,

Int. Cl. G03c1/60, 5/34 US. Cl. 96-75 8 Claims ABSTRACT OF THE DISCLOSURE A heat-developable diazotype material of improved shelf life and ready developability is prepared by providing a two-component vapor-permeable diazotype sheet on its reverse side with a composite layered coating which comprises a first layer of a composition including a resinous binder having uniformly dispersed therein finely divided particles of a water-soluble acid amide, and a second layer thereon of a resinous binder having uniformly dispersed therein finely divided particles of a strongly alkaline inorganic base having a relatively low water solubility.

The present invention relates to a two-component diazotype material having a light-sensitive layer containing a diazo compound and a coupling component on a carrier, with the formation of the dyestuif being initiated by the action of heat.

Two-component diazotype materials capable of being Thus for example two-component diazotype materials are known in which the additional layer is applied to the light-sensitive layer as a covering coating. For example, Dutch patent specification 288,596 describes a diazotype material capable of being developed by heat which consists of a carrier with a light-sensitive twocomponent diazotype layer onto which a covering coating has been applied which consists of an organic binder in which salts or addition products of bases and salts which release ammonia or volatile amines on heating have been dispersed. The Dutch patent specification referred to quotes, as substances which produce alkali, organic substances such as for example benzylamino-p-laurylaminobenzoates and inorganic compounds, such as for example magnesium ammonium phosphate. A two-component diazotype material of the same construction is described in Belgian patent specification 647,069. In this case the thin covering layer contains ammonium salts and metal oxides dispersed in an organic binder. The compositions of ammonium sulphate/calcium oxide and ammonium chloride/magnesium oxide are especially stressed as thermolabile systems which yield ammonia.

It is furthermore known to spread the layer which yields the gaseous alkali onto the reverse side of the carrier. In that case the carrier has to be gas-permeable. A copying material of this construction is described in US. Pat. 3,046,128. In this, the diazotype material capable of being developed by heat consists of paper as the carrier, a layer spread thereon which contains a diazo compound and a coupling component, and a layer on the reverse side which preferably contains urea as the thermolabile substance yielding gaseous alkali, the substance being optionally dispersed in a binder.

The diazotype materials of the kind described above which have hitherto become known either have the disadvantage of requiring uneconomically high-temperatures to be used in order to initiate colour formation or of not being sufficiently storage-stable. The former disadvantage applies especially to materials in which the light-sensitive layer and the alkali-yielding layer are present on opposite sides of the carrier. On the other hand the storage stability, especially under tropical conditions, is poor for those materials in which the light-sensitive layer and the alkali-yielding layer are carried on the same side.

The. problem on which the present invention is based therefore was to produce a diazotype material capable of being developed by heat which can be developed at relatively low temperatures and with short heat exposure times and which nevertheless exhibits adequate storage stability even under tropical conditions.

The present invention solves this problem by a diazotype material capable of being developed by heat which consists of a gas-permeable carrier, a light-sensitive covering layer containing at least one diazo compound, at least one coupling component as well as acid additives, and a reverse-side layer which releases a volatile base on heating. The copying material is characterized by the reverse-side layer consisting of two layers with the inner layer, which is in direct contact with the carrier, consisting of at least one water soluble acid amide of ammonia or a volatile amine, and a binder, and the outer layer consisting of at least one inorganic base of relatively low solubility in water, such as for example calcium hydroxide or sodium aluminate, and a binder.

Paper is preferably used as the carrier. However, woven and non-woven textiles as well as gas permeable films, such as for example cellulose hydrate films, cellulose acetate films and polyamide films may also be used as carrier materials as long as they are thin enough.

The light-sensitive two-component covering layer may typically contain any of the known combinations of diazo compounds and coupling components. As a result all known two-component diazotype materials capable of being developed dry may be used as starting materials for the diazotype material of the invention. Commercially available diazotype sheets may therefore be directly coated with the developer combinations according to the present invention to provide useful heat-developable diazotype materials. Since the weight per unit area of the reverseside coating only amounts to about 20 g./ sq. m., with the inner layer contributing about 15 g./ sq. m and the outer layer 5 g./sq. m., the copying material of the invention is visually indistinguishable from the known two-component diazotype material for dry development. The weights per surface area which have been quoted represent means values which may be considerably exceeded or reduced.

As acid amides which may be used in the inner layer of the reverse-side coating there may be named, inter alia, the amides of acetic acid, of mono-, diand trichloroacetic acid, the monoand diamides of oxalic and fumaric acid, and, preferably, the monoamides, or the monoor diamides, of hydroxycarboxylic acids, such as for example succinic acid, glycolic acid, malic acid, tartaric acid, citric acid and lactic acid. Particularly useful are such amides as are capable of being saponi'fied easily under alkaline conditions and thereupon preferably yield ammonia or low aliphatic amines having up to 6 C-atoms in one substituent, such as, for example, monomethylamine, dimethylamine, methylethylamine or monocyclohexylamine.

Diamides of sulphuric acid are also preferred, especially sulphurylamide and compounds of general formula:

in Which R R and R may be identical or different and may be hydrogen, or alkyl, aralkyl, acyl, carbaminyl and carboxyl residues having up to 6 C-atoms.

These compounds are easily soluble in water and crystallise on evaporation of the water. As experience has shown, such substances are particularly suitable since a microcrystalline distribution of the acid amides in the inner layer of the reverse-side coating shows particularly good results.

Hydrophobic high polymers, such as for example polyvinyl acetate, are preferred as the binders for the acid amides. These binders are generally used as aqueous dispersions, with the acid amide being dissolved in the aqueous phase. The mixing ratio of acid amides and binder should lie within the range of 0.1 to 0.5 part by weight of binder per part by weight of acid amide.

Inorganic bases with the requisite low water solubility which may be used in the outer layer of the reverse side coating of the copying material of the invention are primarily oxides and hydroxides of the alkaline earth metals as well as the metal salts of weak or medium strength acids which dissolve partially or completely in an aqueous medium to give a strongly alkaline reaction. In addition to the oxides and hydroxides of calcium, strontium and barium, their carbonates, borates, silicates and secondary and tertiary phosphates are, for example, suitable. Aluminates, stannates and zincates, especially of sodium and potassium, are also suitable.

Suitable binders for the above named inorganic bases are, for example, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, polyvinyl formal, polyvinyl butyral, but especially ethylcelluose of medium viscosity. The mixing ratio of binder to inorganic base should lie Within the range of 0.1 to 0.5 :1 part by weight. The binders are preferably applied from a solution in which the inorganic bases have been finey dispersed. Possible solvents are, for example, benzene, toluene, methylene chloride, trichloroethylene, ethyl acetate or butyl acetate.

The heat-sensitive diazotype material of the invention now indeed stands out compared to the known diazotype materials capable of being developed by heat and having a separate alkali-yielding layer in that it can be completely developed at temperatures between 90 and 120 C. within a short time and nevertheless is storage-stable even at high relative atmospheric humidities, such as especially occur in the tropics over prolonged periods.

The developed copies have exceptionally good contrast and give intensely coloured images on a White background. The copies are equally as good as those which have been developed by the conventional dry process, for example by the use of ammonia vapors.

It has been found that the advantages of the present invention depend on one condition: water or water vapour has to be present in the copying material during the development process. Since the requisite amounts of Water are very low, the water may, for example, suflice which is present in the atmosphere at relative atmospheric humidities of more than 60%, as may the water 'which is adsorptively bound to the fibres of the paper as long as the amount of water is more than about 5% by weight relative to the weight of the paper. An adequate amount of 'water is however not always present. A preferred embodiment of the copying material of the invention therefore contains in the outermost layer of the reverse side coating a substance which releases Water or water vapour on heating to temperatures of between 90 and 120 C.

Suitable water-releasing substances are, for example, inorganic crystal hydrates which spontaneously or successively release their water within the development temperature range. Strontium chloride containing water of crystallisation (SrCl -6H O) is especially suitable. Furthermore polyhydric aliphatic alcohols which are completely miscible with water, such as for example ethylene, propylene and butylene glycols and preferably, glycerine, are suitable. These are used at a water content of 5 to 10% by weight. The alcohols are dispersed in the coating solution so that the coating produced therefrom also contains them in a finely divided form, but not molecularly dispersed. Depending on the solubility of the alcohol in the solvent of the coating solution for the outermost layer of the reverse side coating a certain amount of molecularly dispersed distribution naturally always also occurs. Water-yielding substances which may be used are, furthermore, micro-capsules containing water whose e11- capsulating substances are hydrophobic polymers which are particularly insoluble in the organic solvent vehicle of the outer coating composition. These water-containing micro-capsules burst at the development temperature whereupon the water enclosed within them is liberated. At times it is also possible to introduce the water together with the inorganic base, as for example in the case of strontium hydroxide containing water of crystallisation (Sr(OH) -8H O).

According to the invention the reverse side outer coating should contain so much water-yielding material as to liberate 0.02 to 0.5 part by weight of water per 1 part by weight of inorganic base.

The manufacture of the diazotype material of the invention employs common coating practices and techniques.

A preferred procedure is to twice coat the reverse side of a normal dry-developing two-component diazotype material with the appropriate solutions or dispersions. The acid amides are preferably applied to the reverse side of the carrier from a neutral or weakly acid aqueous solution containing about 15 to 25% by volume of an aqueous plastic dispersion. The application is carried out by means of known coating processes. Thereafter the material is dried at to C. Immediately after drying the second coating containing the inorganic base is then applied. Here, as already mentioned, one does not use an aqueous coating solution, but a solution based on an organic solvent. Application from an organic solvent is required since coupling would immediately start if an aqueous solution were to be applied.

It has proved useful to prevent the light-sensitive preparation from penetrating into the carrier, and hence making contact with the reverse side coating, by using suitable dispersion primers. Suitable dispersion primers are for example aqueous dispersions of finely divided surfaceactive silica in an organic hydrophobic polymer as the binder.

The formation of images with the diazotype material of the invention is simple and takes place in the usual manner. After image-Wise exposure of the copying material under the original, the copying material is warmed to temperatures of between and C. and left at this temperature for 5 to 30 seconds. The heating may for example take place by means of heated plates or rollers or A white base paper of the type usual in diazotype practice is primed on one side with an aqueous suspension of finely divided silica and polyvinyl acetate and is dried. Thereafter the same side of this paper is coated with an aqueous solution consisting of Parts by weight Water 100 Ethylene glycol l Citric acid 3 Zinc chloride Thiourea 5 Saponin 0.02 2,3 dihydroxynaphthalene 6 sulphonic acid (Na 3 salt) Double salt of 4-N,N-diethylaminobenzene diazonium chloride and zinc chloride and dried at 70-80 C.

The reverse side of the paper coated in this way has applied to it to a dry weight of about g./sq.m. an aqueous solution consisting of Parts by weight Water 50 Aqueous polyvinyl acetate dispersion 15 Sulphurylamide 50 which is dried at 70-80 C. This dried coating is then coated to a dry weight of about 5 g./sq.m. with a suspension obtained by grinding 15 parts by weight of calcium hydroxide 8 parts by weight of glycerine with 10% by weight water, in

100 parts by weight of methylene chloride, in which 5 parts by weight of ethylcellulose have been dissolved. On drying at 30 to 40 C. a thin film in which calcium hydroxide and glycerine are finely dispersed forms on the reverse side of the paper.

The suspension is produced by grinding in a ball mill or colloid mill, with a comminution of the inorganic base down to a particle size of about 515 m being required in order to achieve a smooth reverse side of the paper and optimum development conditions.

A sheet of the diazotype paper produced in this manner is given an image-wise exposure in a common diazotype copying device in contact underneath a transparent original until the diazo-compound has been bleached under the light-transmitting areas of the original, and is then developed between two metal plates heated to 110 115 C. The copy so obtained has exceptionally rich contrast and exhibits an intense slightly violet-toned dark blue azodyestuff image on a clear white background.

If development takes place by means of ammonia gas the image of the copy shows the same colour. The diazotype material is exceptionally storage-stable under normal and damp climatic conditions.

EXAMPLE 2 A white base paper of the type usual in diazotype practice is primed on one side with an aqueous dispersion of finely divided silica and casein, dried, and thereafter coated on the same side with an aqueous solution of the following composition;

Parts by weight Sulphamic acid 2 Urea S Thiourea 5 Zinc chloride 2.5

2,3 dihydroxynaphthalene-6-sulphonic acid (Na salt) 2.5 Phloroglucinol 0.3 Double salt of 4-N,N-diethylaminobenzene diazonium chloride and zinc chloride 2.5 Water The sensitized paper is dried and the paper reverse side subsequently coated as in Example 1.

A sheet of the diazotype paper produced in this manner is given an image-wise exposure under an original and developed as in Example 1. A copy having black azo dyestufi images on a white background is obtained in a short time. If development is carried out with ammonia gas the images of the copy show the same colour.

The storage stability of the diazotype paper produced in this way is very good under normal and damp warm conditions.

EXAMPLE 3 White base paper of the type usual in diazotype practice is coated on one side with an aqueous finely divided silica dispersion, dried, coated on the same side with an aqueous solution of Lactic acid amide 50 Polyvinyl acetate dispersion 15 Water 50 is applied to the reverse side of the paper which has been sensitized in this Way, and is dried. Thereafter a suspension of 15 parts by weight of calcium hydroxide 10 parts by weight of strontium chloride containing water of crystallisation (SrCl 6H O), in

parts by weight of methylene chloride, in which 5 parts by weight of ethylcellulose have been dissolved is applied to the reverse side and the paper which has been coated in this way is dried at 30-40 C.

A sheet of the highly light-sensitive diazotype paper produced in this way is given an image-wise exposure and developed as in Example 1. The copy exhibits an intense violet-blue image on a white background.

The diazotype paper has good stability under normal humidity conditions.

EXAMPLE 4 A base paper of the type usual in diazotype is primed on one side with an aqueous suspension of finely divided silica and polyvinyl acetate, dried, and thereafter coated on the same side with an aqueous solution of the following composition:

Parts by weight Citric acid 0.75 Zinc chloride 5.0 Thiourea 5.0

Parts by weight Saponin 0.02 2,3-dihydroxynaphthalene 6 sulphonic acid (Na salt) Double salt of 4-N-ethyl-N-2'-hydroxyethyl-benzenediazonium chloride and zinc chloride 1.4 Ethylene glycol 10 Water 100 After drying, a solution of Parts by weight Water 50 Aqueous polyvinyl acetate dispersion l5 Sulphurylamide 30 is applied to the reverse side of the paper, the paper is again dried, and the primed reverse side thereafter coated with a suspension obtained by grinding parts by weight of sodium aluminate in 100 parts by weight of trichlorethylene, in which 10 parts by weight of polyvinyl acetate resin have been dissolved.

On drying at 30-40 C. a thin film in which the sodium aluminate is finely dispersed forms on the reverse side of the paper.

A sheet of the diazotype paper so obtained is given an image-wise exposure and developed in a damp atmosphere between two metal plates heated to 110-1 C. The copy shows an intense violet-toned blue image on a white background. On development with ammonia gas a copy with a violet-toned blue image on a white background is also obtained.

The diazotype paper has good storage stability both under normal and under damp climatic conditions.

EXAMPLE 5 White base paper of the type usual in diazotype practice is primed on one side with an aqueous dispersion of finely divided silica and polyvinyl acetate, and thereafter the same side is coated with an aqueous solution of the following composition:

Parts by weight Tartaric acid 2.5

Aluminium sulphate 1.5

Saponin 0.02 2,3-dihydroxynaphthalene 5 sulphonic acid (Na salt) Double salt of 4-N-ethylamino-3-methylbenzenediazonium chloride and zinc chloride 1.5

Water 100 The sensitized paper is dried in the usual manner, the

reverse side subsequently coated with a solution of Parts by weight Lactic acid amide 50 Polyvinyl acetate dispersion 15 Water 50 the coating dried, and the reverse side provided with a finely divided suspension obtained by grinding 15 parts by weight of strontium hydroxide (Sr(OI-I) -8H O) in 100 parts by weight of methylene cholride, in which 5 parts by weight of ethylcellulose have been dissolved.

8 and images of the same colour is obtained. The diazotype paper has good stability under normal and damp climatic conditions.

EXAMPLE 6 White base paper of the type usual in diazotype practice, which has been coated on one side with an aqueous silica dispersion and subsequently dried, is coated on the same side with an aqueous solution of the following composition:

Parts by weight Tartaric acid 2.5 Aluminium sulphate 1.5 Saponin 0.02 2,3-dihydroxynaphthalene-fi-sulphonic acid (Na salt) 3.0 Double salt of 4-pyrrolidino-3-(3-diethylamino-2- hydroxy)propoxy-benzenediazonium chloride and zinc chloride 1.5 Water After drying in the usual way the reverse side of the paper is coated with a solution of Parts by weight Water 50 Aqueous polyvinylacetate dispersion 15 Sulphurylamide 50 and dried. Thereafter the reverse side has applied to it a finely divided suspension obtained by grinding 15 parts by weight of barium oxide in 100 parts by weight of trichlorethylene, in which 5 parts by weight of ethylcellulose have been dissolved.

On drying at 30-40 C. a thin film in which the barium oxide is finely dispersed forms on the paper reverse side.

A sheet of the highly light-sensitive diazotype paper produced in this way is given an image-wise exposure and is developed in a damp atmosphere between two metal plates heated to -115 C. The copy shows a violet image on a white background. A copy of the same diazotype paper developed with ammonia gas shows an image of the same colour.

EXAMPLE 7 Commercially available light-sensitive two-component diazotype paper giving blue copies when developed with ammonia vapors is coated on the reverse side with an aqueous solution of Parts by weight Glycolic acid amide 30 Polyvinylacetate dispersion 15 Water 50 and dried. Thereafter a suspension of 15 parts by weight of calcium hydroxide 7 parts by weight of ethylene glycol containing 5% by weight of water, in

100 parts by weight of methylene chloride, in which 5 parts by weight of ethylcellulose have been dissolved EXAMPLE 8 Commercially available two-component ammonia developable diazotype material producing black copies and of normal light-sensitivity is coated on the reverse side with an aqueous solution of Parts by weight Water 50 Aqueous polyvinylacetate dispersion 15 Sulphurylamide 50 and dried at 7080 C.

The reverse side of the paper which has been treated in this way is further coated with a suspension obtained by grinding On drying at 30-40" C. a thin film in which the cal cium hydroxide and glycerine are finely dispersed is produced on the reverse side of the paper. A sheet of the diazotype material produced in this manner is given an image-wise exposure under a transparent original and is then developed between two metal plates heated to 110- 115 C. A copy of extremely rich contrast is obtained, having deep black image areas on a white background.

A copy developed by means of ammonia gas also shows deep black image areas, again on a white background.

The storage stability of the diazotype paper is very good both at low and high relative atmospheric humidities.

EXAMPLE 9 A base paper of the type usual in diazotype practice is primed on one side with an aqueous dispersion of finely divided silica and casein, and the same side is subsequently coated with an aqueous solution of the following composition:

Parts by weight After drying in the usual manner the reverse side of the paper is coated with a solution of Parts by weight Glycolic acid amide 30 Polyvinylacetate dispersion 15 Water 50 and dried. Thereafter a suspension of 15 parts by weight of barium oxide 15 parts by weight of glycerine 100 parts by weight of trichlorethylene, in which 50 parts by weight of ethylcellulose have been dissolved is applied to the reverse side of the paper which has been coated in this way.

After the usual drying at 30-40" C. a thin film which contains finely divided barium oxide dispersed together with glycerine forms on the reverse side of the paper.

A sheet of the diazotype paper produced in this manner is given an image-wise exposure and is developed as in Example 1.

The copy shows an intense bluish-violet image on a white background and is indistinguishable from a copy developed by means of ammonia gas in respect of both contrast and colour.

The storage stability of the diazotype paper is very good under normal and damp climatic conditions.

The above examples have been presented for the purpose of illustration and should not be taken to limit the scope of the present invention. It will be apparent that the described examples are capable of many variations and modifications which are likewise to be included within the scope of the present invention as set forth in the appended claims.

What is claimed is:

1. Heat-developable diazotype material comprising:

a vapor permeable support;

a coating on the first side of said support comprising a light-sensitive diazonium compound, and an azo coupler compoundl capable of forming a distinct azo dye with said diazonium compound in an alkaline medium, and an acid stabilizing compound;

a first layer coated on the other side of said support comprising a finely-divided Water-soluble acid amide uniformly dispersed in a resinous binder, said amide being capable of releasing ammonia or a volatile amine compound upon heating; and

a second layer coated on said first layer comprising a finely divided strongly alkaline inorganic base having a relatively low solubility in water uniformly dispersed in a resinous binder 2. Material according to claim 1 wherein said acid amide is selected from the group consisting of diamitles of sulphuric acid having the general formula wherein R R and 11 each individually represent hydrogen, or an alkyl, aralkyl, acyl, carbaminyl or carboxyl residue; lactic acid amide, and glycol acid amide.

3. Material according to claim 1 wherein said second layer comprises a binder and, uniformly dispersed therein, finely divided particlesbf (a) a strongly alkaline inorganic base and (b) a water ,generator active in the temperature range of about -120 (2., said generator being present in an amount sufiicient to provide 0.02 to 0.5 part by weight of water per part of inorganic base.

4. Material according to claim 1 wherein said inorganic base is selected from the group consisting of calcium hydroxide, sodium aluminate, strontium hydroxide, and barium oxide.

5. Material according to claim 3 wherein said inorganic base is selected from the group consisting of calcium hydroxide, sodium aluminate, strontium hydroxide, and barium oxide; and said water generator is selected from the group consisting of inorganic salts having heat dissociable waters of crystallzation, and heat-rupturable water-containing microcapsules.

6. Material according to claim 3 wherein said inorganic base is calcium hydroxide, and said water generator is strontium chloride (SrCl 6H O) 7. Material according to claim 1 wherein said amide is sulfurylamide, and said inorganic base is sodium aluminate 8. Material according to claim 1 wherein said amide is lactic acid amide, and said inorganic base is strontium hydroxide (Sr(OH) -8H O).

References Cited UNITED STATES PATENTS 2,313,288 3/1943 Barde 96-49 2,178,771 11/1939 Alink et al 969l 3,046,128 7/1962 Klimkowski et al. 9691 XR 3,076,707 2/ 1963 Lawton et al. 9675 3,255,007 6/1966 Kosar 96-91 XR 3,318,699 3/1967 Lind 96-49 3,360,371 12/1967 Munder et al. 96-91 3,434,838 3/1969 Munder et al. 96-49 3,453,112 7/1969 Schaelfer 9691 (Other references on following page) 1,379,066 6,404,649 1,070,625 983,665 1,045,714 1,092,293 1,127,237 Ad. 78,679 1,336,607 Ad. 83,978 1,418,156

FOREIGN PATENTS France. Netherlands. Great Britain. Great Britain. Great Britain. Great Britain. Great Britain. France. France. France. France.

OTHER REFERENCES Chem. Abstracts, vol. 65, 1966, 4910a. Dietzgen, J. E.: Reproduction Review," February 1962, pp. 14, 15, 22 and 26.

NORMAN G. TORCHIN, Primary Examiner C. BOWERS, Assistant Examiner US. 01. X.R. 

